It is wise that you are asking about this as these 2 exercises while valuable can become less so or even dangerous if done wrong.
My quick tips would be for the bench, hold you shoulders down (toward your feet) and back through the whole motion and for now I'd keep my elbows about halfway between parallel to the bar and down at your sides. Maybe a little higher. Grip the bar so that when you are at the bottom of the movement your forearms are very close to straight up and down. This would mean a bit wider than shoulder width at the top. Also don't drift toward your feet or your head. Straight down to the chest and straight back up.
For the squat I'd stand at a shoulder width stance or a little wider with your toes pointing at whatever angle outward makes it comfortable for your knees to go straight out over your feet. Practice with no weight. If you feel your toes trying to twist out, point them out some more. It's very important that you not allow your knees to bow in or out. Your knees should hide your feet as you go down, at least for now. There are variations where you wouldn't let your knees go that far forward, but don't worry about that for now.
Your back should absolutely remain arched and straight, but not to the point where you're forcing the arch too far back. All the way down and all the way up on every rep your back needs to stay that way or you are an injury waiting to happen. Do not let your back bow forward. Make sure the bar is on your upper back (trapezius) and not your neck or too far down your back. Hold your hands on the bar close enough together so that you naturally create a sort of platform for the bar to rest on by pulling your shoulders back without shrugging. If it hurts your spine, stop. You may need to practice this with just the bar too until you get it down.
Start by going down to at least the point where your thighs are parallel to the floor. If you catch on fast to the rest of this try going all the way down til your butt touches your heels.
On both of these exercises DO NOT get overly ambitious until you know what you're doing by going too heavy. You're not going to make progress if you hurt your self.
If it's at all possible find somebody with some experience to help you learn these and other exercises properly. We all started somewhere and there should be somebody where you train, unless you train at home, who would be willing to lend a hand. In any case these are skills that need to be learned so be patient and keep it and one day it will all be second nature.
Whew, didn't mean to go that long, but hope that helps.